Development of GEM detector for tokamak SXR tomography system: Preliminary laboratory tests

he GEM based detecting system is currently being developed for poloidal tomography to be used at WEST project tokamak. It consists of two GEM detectors of planar and of cylindrical geometry for the vertical and horizontal ports, respectively. Several laboratory tests were conducted to assess the performance of the prototype detectors and verify the proposed design. For that, the measurements of the detectors with 55Fe source and X-ray generator were performed. The detector’s behavior was tested for two gas mixtures: Ar/CO2 and Ar/CO2/CF4 and the detector amplification dependencies on high photon flux, start-up and applied high voltages are demonstrated. The cluster sizes of the generated anode charge and energy resolution are also provided

Overview of the JET results

Since the installation of an ITER-like wall, the JET programme has focused on the consolidation of ITER design choices and the preparation for ITER operation, with a specific emphasis given to the bulk tungsten melt experiment, which has been crucial for the final decision on the material choice for the day-one tungsten divertor in ITER. Integrated scenarios have been progressed with the re-establishment of long-pulse, high-confinement H-modes by optimizing the magnetic configuration and the use of ICRH to avoid tungsten impurity accumulation. Stationary discharges with detached divertor conditions and small edge localized modes have been demonstrated by nitrogen seeding. The differences in confinement and pedestal behaviour before and after the ITER-like wall installation have been better characterized towards the development of high fusion yield scenarios in DT. Post-mortem analyses of the plasma-facing components have confirmed the previously reported low fuel retention obtained by gas balance and shown that the pattern of deposition within the divertor has changed significantly with respect to the JET carbon wall campaigns due to the absence of thermally activated chemical erosion of beryllium in contrast to carbon. Transport to remote areas is almost absent and two orders of magnitude less material is found in the divertor